linux-toradex.git/Documentation/cpu-freq/cpu-drivers.txt, branch v4.16

cpufreq: Add and use cpufreq_for_each_{valid_,}entry_idx()

2018-02-08T09:21:39+00:00

Pointer subtraction is slow and tedious. Therefore, replace all instances
where cpufreq_for_each_{valid_,}entry loops contained such substractions
with an iteration macro providing an index to the frequency_table entry.

Suggested-by: Al Viro 
Link: http://lkml.kernel.org/r/20180120020237.GM13338@ZenIV.linux.org.uk
Acked-by: Viresh Kumar 
Signed-off-by: Dominik Brodowski 
Signed-off-by: Rafael J. Wysocki

Documentation: cpu-freq: cpu-drivers: Fix repetition of word 'to'

2017-03-09T09:43:34+00:00

The patch replaces 'to to' with 'to' in the documentation.

Signed-off-by: sayli karnik 
Acked-by: Viresh Kumar 
Signed-off-by: Jonathan Corbet

cpufreq: Documentation: Updates based on current code

2017-02-03T22:59:40+00:00

The cpufreq core has gone though lots of updates in recent times, but on
many occasions the documentation wasn't updated along with the code.
This patch tries to catchup the documentation with the code.

Also add Rafael and Viresh as the contributors to the documentation.

Based on a patch from Claudio Scordino.

Signed-off-by: Claudio Scordino 
Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

cpufreq: Return index from cpufreq_frequency_table_target()

2016-06-08T22:58:06+00:00

This routine can't fail unless the frequency table is invalid and
doesn't contain any valid entries.

Make it return the index and WARN() in case it is used for an invalid
table.

Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

cpufreq: Drop freq-table param to cpufreq_frequency_table_target()

2016-06-08T22:58:06+00:00

The policy already has this pointer set, use it instead.

Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

cpufreq: Unexport cpufreq_frequency_table_cpuinfo()

2016-06-02T21:24:41+00:00

All cpufreq drivers with a freq-table are migrated to use
cpufreq_table_validate_and_show() long back and the routine
cpufreq_frequency_table_cpuinfo() isn't used outside of cpufreq core
now.

Unexport it and update Documentation as well.

Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

cpufreq: add support for intermediate (stable) frequencies

2014-06-05T21:32:29+00:00

Douglas Anderson, recently pointed out an interesting problem due to which
udelay() was expiring earlier than it should.

While transitioning between frequencies few platforms may temporarily switch to
a stable frequency, waiting for the main PLL to stabilize.

For example: When we transition between very low frequencies on exynos, like
between 200MHz and 300MHz, we may temporarily switch to a PLL running at 800MHz.
No CPUFREQ notification is sent for that. That means there's a period of time
when we're running at 800MHz but loops_per_jiffy is calibrated at between 200MHz
and 300MHz. And so udelay behaves badly.

To get this fixed in a generic way, introduce another set of callbacks
get_intermediate() and target_intermediate(), only for drivers with
target_index() and CPUFREQ_ASYNC_NOTIFICATION unset.

get_intermediate() should return a stable intermediate frequency platform wants
to switch to, and target_intermediate() should set CPU to that frequency,
before jumping to the frequency corresponding to 'index'. Core will take care of
sending notifications and driver doesn't have to handle them in
target_intermediate() or target_index().

NOTE: ->target_index() should restore to policy->restore_freq in case of
failures as core would send notifications for that.

Tested-by: Stephen Warren 
Signed-off-by: Viresh Kumar 
Reviewed-by: Doug Anderson 
Signed-off-by: Rafael J. Wysocki

cpufreq: Introduce macros for cpufreq_frequency_table iteration

2014-04-29T22:05:31+00:00

Many cpufreq drivers need to iterate over the cpufreq_frequency_table
for various tasks.

This patch introduces two macros which can be used for iteration over
cpufreq_frequency_table keeping a common coding style across drivers:

- cpufreq_for_each_entry: iterate over each entry of the table
- cpufreq_for_each_valid_entry: iterate over each entry that contains
a valid frequency.

It should have no functional changes.

Signed-off-by: Stratos Karafotis 
Acked-by: Lad, Prabhakar 
Acked-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki

cpufreq: Add stop CPU callback to cpufreq_driver interface

2014-03-20T02:50:12+00:00

This callback allows the driver to do clean up before the CPU is
completely down and its state cannot be modified.  This is used
by the intel_pstate driver to reduce the requested P state prior to
the core going away.  This is required because the requested P state
of the offline core is used to select the package P state. This
effectively sets the floor package P state to the requested P state on
the offline core.

Signed-off-by: Dirk Brandewie 
[rjw: Minor modifications]
Signed-off-by: Rafael J. Wysocki

cpufreq: Implement light weight ->target_index() routine

2013-10-25T20:42:24+00:00

Currently, the prototype of cpufreq_drivers target routines is:

int target(struct cpufreq_policy *policy, unsigned int target_freq,
		unsigned int relation);

And most of the drivers call cpufreq_frequency_table_target() to get a valid
index of their frequency table which is closest to the target_freq. And they
don't use target_freq and relation after that.

So, it makes sense to just do this work in cpufreq core before calling
cpufreq_frequency_table_target() and simply pass index instead. But this can be
done only with drivers which expose their frequency table with cpufreq core. For
others we need to stick with the old prototype of target() until those drivers
are converted to expose frequency tables.

This patch implements the new light weight prototype for target_index() routine.
It looks like this:

int target_index(struct cpufreq_policy *policy, unsigned int index);

CPUFreq core will call cpufreq_frequency_table_target() before calling this
routine and pass index to it. Because CPUFreq core now requires to call routines
present in freq_table.c CONFIG_CPU_FREQ_TABLE must be enabled all the time.

This also marks target() interface as deprecated. So, that new drivers avoid
using it. And Documentation is updated accordingly.

It also converts existing .target() to newly defined light weight
.target_index() routine for many driver.

Acked-by: Hans-Christian Egtvedt 
Acked-by: Jesper Nilsson 
Acked-by: Linus Walleij 
Acked-by: Russell King 
Acked-by: David S. Miller 
Tested-by: Andrew Lunn 
Signed-off-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki